.\" Copyright (c) 2015 Dmitry Vagin <daemon.hammer@ya.ru>
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.Dd October 29, 2015
.Dt NG_CHECKSUM 4
.Os
.Sh NAME
.Nm ng_checksum
.Nd reconstructing IP checksums node type
.Sh SYNOPSIS
.In netgraph/ng_checksum.h
.Sh DESCRIPTION
The
.Nm checksum
node can calculate, or prepare for calculation in hardware,
IPv4 header, TCP and UDP checksums.
.Sh HOOKS
This node type has two hooks:
.Bl -tag -width ".Va out"
.It Va in
Packets received on this hook are processed according to settings specified
in config and then forwarded to the
.Ar out
hook, if it exists and is connected.
Otherwise they are reflected back to the
.Ar in
hook.
.It Va out
Packets received on this hook are forwarded to the
.Ar in
hook without any changes.
.El
.Sh CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
.Bl -tag -width foo
.It Dv NGM_CHECKSUM_SETDLT Pq Ic setdlt
Sets the data link type on the
.Va in
hook.
Currently, supported types are
.Cm DLT_RAW
(raw IP datagrams) and
.Cm DLT_EN10MB
(Ethernet). DLT_ definitions can be found in the
.In net/bpf.h
header.
Currently used values are
.Cm DLT_EN10MB
= 1 and
.Cm DLT_RAW
= 12.
.It Dv NGM_CHECKSUM_GETDLT Pq Ic getdlt
This control message obtains the data link type on the
.Va in
hook.
.It Dv NGM_CHECKSUM_SETCONFIG Pq Ic setconfig
Sets the node configuration.
The following
.Vt "struct ng_checksum_config"
must be supplied as an argument:
.Bd -literal -offset 4n
struct ng_checksum_config {
	uint64_t	csum_flags;
	uint64_t	csum_offload;
};
.Ed
.Pp
The
.Va csum_flags
can be set to any combination of CSUM_IP, CSUM_TCP, CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6
(other values are ignored) for instructing the node to calculate the corresponding checksum.
.Pp
The
.Va csum_offload
value can be set to any combination of CSUM_IP, CSUM_TCP, CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6
(other values are ignored) for instructing the node what checksums should be requested from the hardware.
.Pp
The node also takes into account any combination of
CSUM_IP, CSUM_TCP, CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6 already
flagged on the mbuf.
.It Dv NGM_CHECKSUM_GETCONFIG Pq Ic getconfig
This control message obtains the current node configuration returned as a
.Vt "struct ng_checksum_config" .
.It Dv NGM_CHECKSUM_GET_STATS Pq Ic getstats
Returns node statistics as a
.Vt "struct ng_checksum_stats" .
.It Dv NGM_CHECKSUM_CLR_STATS Pq Ic clrstats
Clear the node statistics.
.It Dv NGM_CHECKSUM_GETCLR_STATS Pq Ic getclrstats
This command is identical to
.Dv NGM_CHECKSUM_GET_STATS ,
except that the statistics are also atomically cleared.
.El
.Sh SHUTDOWN
This node shuts down upon receipt of a
.Dv NGM_SHUTDOWN
control message, or when all hooks have been disconnected.
.Sh EXAMPLES
.Xr ngctl 8
script:
.Bd -literal -offset 4n
/usr/sbin/ngctl -f- <<-SEQ
	msg checksum-1: setdlt 1
	msg checksum-1: setconfig { csum_flags=0 csum_offload=6 }
SEQ
.Ed
.Pp
Set the data link type to
.Cm DLT_EN10MB
(Ethernet), do not set additional checksum flags
and request that the hardware calculate CSUM_IP_UDP|CSUM_IP_TCP.
.Sh SEE ALSO
.Xr netgraph 4 ,
.Xr ng_patch 4 ,
.Xr ngctl 8
.Sh HISTORY
The
.Nm
node type was implemented in
.Fx 10.2
and first submitted in
.Fx 12.0 .
.Sh AUTHORS
.An "Dmitry Vagin" Aq daemon.hammer@ya.ru .
